Bob Diamond is due be grilled later today by MPs at the Parliament's Select Committee a day after resigning as Barclays chief, in the wake of the inter-bank interest rate-fixing scandal.MPs are also likely to ask about the role of the Bank of England and the previous government in the rate-fixing. There have been suggestions the Bank of England's Deputy Governor and senior Whitehall officials knew rates were manipulated.Marcus Agius who also tended his resignation but is the care taker Chief exec of Barclays explained about yesterday's disclosure to the treasure select committee.The Libor inter-bank rate plays a key role in global markets, affecting what banks, businesses and individuals pay to borrow money. Manipulating the rate might have given the impression that Barclays - and other banks also thought to have used the practice - was in a stronger financial position than it was.